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Selected Pyrotechnic Publications of K. L. and B. J. Kosanke Page 872

An earlier version appeared in: Journal of Pyrotechnics, No. 24, 2006.

An Evaluation of Lightning Thermo TubeTM

As a Pyrotechnic Ignition System

K. L. and B. J. Kosanke PyroLabs, Inc., Whitewater, CO USA

ABSTRACT

Lightning Thermo Tube (LTT) is a recently in-troduced type of shock tube with characteristics that make it suitable for use with common pyro-technics. LTT is reliably initiated by reasonably energetic electric matches and reliably ignites most pyrotechnic compositions. LTT is physically strong, easily spliced and branched, and is highly weather resistant. LTT produces a moderately bright flash of light upon functioning, which may be a useful effect in itself. This paper presents the results of a series of tests performed to determine some of the more important capabilities and characteristics of LTT as it relates to use with py-rotechnics in general and fireworks in particular.

Introduction

Lightning Thermo TubeTM[1,2] has recently been introduced to the US firework trade. The product is very similar in appearance to conven-tional shock tube.[3–5] However, because of the pyrotechnic used in its manufacture, it does not require the flame-to-shock and shock-to-flame converters that regular shock tube needs when used with typical pyrotechnics.[6] This makes it more convenient and cost effective to use with pyrotechnics than conventional shock tube. Fortu-nately, Lightning Thermo Tube (LTT) retains the safety characteristics, and the ease of splicing and branching of conventional shock tube.

This article reports on an initial brief evalua-tion of LTT for use with pyrotechnics, specifically fireworks and proximate audience pyrotechnics. However, because of the limited scope of this study, for the most part reliability issues are not thoroughly addressed. For example, LTT was def-initely found to have the capability of being initi-ated with commonly used electric matches and with small exploding charges. A reasonably high level of reliability was found in ignition trials with

one type of electric match, where 35 of 35 at-tempts were successful. However, because only a limited number of trials were run, it is not possible to state with confidence how reliably such initia-tion can be accomplished. In many other cases, because even fewer trials were conducted, the re-sults are not statistically significant. Finally, all trials were conducted under moderate environ-mental conditions (i.e., at a temperature of ap-proximately 15 °C (60 °F) and a relative humidity of less than 40%); therefore, it is possible that the performance of LTT under more extreme condi-tions may be different.

The Product

A small coil of Lightning Thermo Tube (LTT) is shown in Figure 1. It is a thick-walled and strong (high tensile strength) plastic tube, approx-imately 3 mm (1/8 in.) in outside diameter and approximately 1.2 mm (0.05 in.) in inside diame-ter. The inside of the tubing has been coated with a thin layer of pyrotechnic composition, which

Figure 1. A photograph of a small coil of Light-ning Thermo Tube (LTT) and items used in cou-pling and splitting LTT. [Each small square is 2.5 mm (0.1 in.)].


propagates an energetic chemical reaction at a high speed and can ignite various other pyrotech-nic materials. Also shown in Figure 1 are three short lengths of rubber tubing and a small plastic tee that can be used to couple and branch the LTT.

The stable propagation rate of LTT was meas-ured and found to be approximately 1100 m/s (3600 ft/s), which is reasonably consistent with its reported propagation rate of 1200 m/s.[7] This measurement was accomplished by video record-ing the propagation of a length LTT at the rate of 20,000 frames per second (see Figure 2).[8] (In Figure 2 and other figures of reacting LTT, the intensity of the light produced by the propagating LTT reaction in relation to the video camera set-tings was so intense as to give the false appear-ance that the diameter of the flash reaction greatly exceeds the actual diameter of the LTT tube.) Us-ing these same video images, it was also deter-mined that approximately 0.2 ms and approxi-mately the first 200 mm (8 in.) of propagation in the LTT were required before the propagation rate stabilized and the full intensity of the propagation was established when initiated with an electric match (Martinez Specialties’ E-Max electric match[9]) using an 8 J capacitive discharge firing set. It is likely that the initiation method may af-fect the run-up distance but almost certainly not the steady state propagation rate.

Figure 3 is an electron micrograph of the end of a piece of LTT cut at an angle to better expose its interior for imaging. (Unfortunately in this two-dimensional image, the thin coating on the inside wall of the tubing somewhat gives the erro-neous appearance that the inner bore of the tube is completely filled with composition.) The Material Safety Data Sheet for LTT[10] lists as its hazardous ingredients, potassium perchlorate and aluminum. The X-ray energy dispersive spectrum (above an energy of 0.5 keV) of a sample of the powder coating (see Figure 4) also includes substantial peaks for iron. In comparing this information, the measured propagation rate for the LTT of approx-imately 1100 m/s (3600 ft/s), and information from the US Patent upon which the LTT is appar-ently based,[2] suggests that the pyrotechnic com-position of the interior wall coating is that given in Table 1.

Figure 2. A collection of 15 images of the propa-gation of LTT after initiation with an electric match. The elapsed time between images is 0.00005 second. (The image width is approxi-mately 800 mm, 32 inches.)

Figure 3. An electron micrograph of a small segment of LTT cut at an angle of approximately 45º to better expose the powder coating on the interior wall of the tube.


0

10

20

30

40

50

60

70

0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5

Energy (keV)

SQ

RT

Co

unt

sAl

Si Cl KK

S

Fe

Fe

Figure 4. The X-ray energy dispersive spectrum of a sample of LTT’s interior powder coating. (SQRT Counts is the square root of the number of counts per energy channel.)

Table 1. Apparent Chemical Formulation of the Internal Powder Coating Used in LTT.

Ingredient PercentageAluminum 50 Iron(II-III) oxide 24.5 Potassium perchlorate 24.5 Talc 1

Because the reported amount of pyrotechnic content is so low (8 mg/m [10]) Lightning Thermo Tube is classed by the US Department of Trans-portation as “not regulated as an explosive” and can be shipped as non-hazardous material,[11] which is the same classification as for the plastic tubing without the pyrotechnic coating on its inte-rior wall. Nonetheless, the US Bureau of Alcohol, Tobacco, Firearms and Explosives is requiring that LTT only be sold to licensees and that it be stored as a regulated material, including a re-quirement for magazine storage and record keep-ing.[7]

Figure 5 is one frame from a standard (NTSC) frame-rate video that demonstrates the projection of fire and sparks emanating from the end of LTT as it functions. The functioning thermo tube is seen as the narrow bright band at the extreme left in the image. The fire output from the LTT is seen to expand to a diameter of approximately 25 mm (1 in.) and to extend to approximately 100 mm (4 in.) to the right. The spray of sparks from the LTT, although not clearly visible in Figure 5, also projects to distance of at least 200 mm (8 in.) from the end of the thermo tube.

Figure 5. A standard frame-rate video image (NTSC) of functioning LTT, where the total width of the image is approximately 250 mm (10 in.).

When conventional shock tube (charged with explosive composition) functions, the pressure developed within the tube will occasionally cause the tube to burst. This is apparently because of some migration and accumulation of powder with-in the shock tube. (Conventional shock tube will fairly reliably burst the tube when two nearly sim-ultaneous shock waves are propagated from both ends of the shock tube to collide along its length.) This type of tube bursting was not observed for LTT during the trials that were conducted, even when opposing shocks were caused to collide within the tubing. (However, based on the limited testing being reported, it should not be assumed that LTT will never burst its tube.)

Similar to shock tube, the functioning of LTT can produce moderately loud sound. The sound pressure level (SPL) produced by the emerging shock front is approximately 145 dB (free field – peak – linear) measured at 1.2 m (4 ft) directly in line with the end of the LTT (i.e., at 0° to the axis of the LTT). Under the same conditions, except measured at 90° to the end of the LTT, the SPL was reduced to approximately 135 dB. The output (blast) from the end of the LTT is the primary source of the sound, as opposed to the sound radi-ating outward through the walls of the tube. Thus, when the ends of the LTT were sealed (or well muffled) the SPL did not exceed the background sound level in the laboratory at the time (i.e., ap-proximately 90 dB).

Initiation Trials

A series of trials were conducted to determine what common stimuli tend to be capable of initiat-ing Lightning Thermo Tube. In many cases only a limited number of individual trials were per-formed; thus one should not infer much about the reliability of the various methods. See Table 2 for a summary of the LTT initiation tests that were


performed. (The order of the information in Ta-ble 2 is not the same as the order in which the tri-als were conducted.) Table 2 begins with three methods that were unsuccessful in producing ini-tiations of LTT on every attempt, then two meth-ods that worked with less than complete reliabil-ity, and finishes with a number of methods that were successful on every attempt.

Table 2. Lightning Thermo Tube Initiation Test Results.

Test Conditions(a) Initiations

/ Trials

Fall-hammer impact (5 kg hammer from a height of 1 m, 39.4 in.)

0 / 10

Propane torch flame applied for five seconds (flame temperature was approximately 1900 ºC)

0 / 3

Fire spit from visco fuse coupled using inert tubing (b) 0 / 5

LTT installed into the wall of a dis-charging consumer fireworks mortar

2 / 4

Luna Tech BGZD electric match[12] coupled using tubing(c) 30 / 35(d)

Martinez Specialties E-Max electric match[9] coupled using tubing(c) 35 / 35

Spark gap using an 8 J capacitive discharge firing unit

30 / 30

Martinez Specialties E-Max electric match coupled using a Martinez Specialties Quick Fire VF Clip[13](c)

3 / 3

Martinez Specialties Exploding-Bridge-Wire initiator coupled using its attached inert tube and an 8 J capacitive discharge firing unit

3 / 3

Bare electric match tip (without any pyrotechnic composition) using an 8 J capacitive discharge firing unit

3 / 3

CCI #209M shot shell primer in a shock tube firing apparatus(e)

3 / 3

Functioning shock tube coupled us-ing tubing

2 / 2

Approximately 50 mg of flash pow-der in coupling tube, ignited with visco fuse

3 / 3

a) Trials were conducted at a temperature of approxi-mately 15 °C (60 °F) and a relative humidity of less than 40%.

b) Visco fuse is a thread wrapped Black Powder fuse approximately 2.5 mm (3/32 in.) in diameter and is also called hobby, cannon and firework safety fuse.

c) The electric match was fired using either an 8 J ca-pacitive discharge firing set or one using a 5 V power supply.

d) The first 25 trials with these electric matches pro-duced 25 successful initiations of the LTT. Howev-er, the last 10 trials only produced 5 successful ini-tiations. At this time it is not known what the reason for this was (e.g., statistics, or some difference in the matches or the LTT). However, the Luna Tech electric matches are noticeably more mild in their functioning than the Martinez Specialties matches that were used with greater success.

e) The US distributor of LTT reports that this is the manufacturer’s recommend method of initiation for LTT.

The trials using fall-hammer impacts (0 initia-tions in 10 trials), the flame from a propane torch (0 initiations in 3 trials) and the fire spit from vis-co fuse (0 initiations in 5 trials) were all unsuc-cessful in initiating the LTT. The setup used to determine the capacity for initiation of LTT using visco fuse, approximately 18 mm (¾ in.) of 3 mm (1/8 in.) ID inert tubing was used to connect the initiation source to the LTT. The initiation source and the LTT were inserted into opposite ends of

ViscoFuse

CouplingTube

LTT

CouplingTube

LTTElectricMatch

ViscoFuse

Coupling TubeLTT

Flash Powder

Figure 6. An illustration of some of the methods used in trials for initiating LTT. Top, visco fuse coupled to LTT. Middle, electric match coupled to LTT. Bottom, visco fuse coupled to flash powder that is then coupled to LTT.


the tubing until contact was made between them. (See the upper illustration in Figure 6.)

The next stronger impetus tried was to mount the end of LTT through the side of a consumer firework mortar and to fire a small aerial shell from the mortar. The combined flame and modest pressure effect that was produced, worked occa-sionally (2 initiations in 4 trials), but only when the aerial shell was propelled with significant force.

The next stronger impetus tried was to use a fairly mildly functioning electric match (Luna Tech’s BGZD electric matches).[12] The first 25 trials using these electric matches produced 25 successful initiations of the LTT. However, the last 10 trials only produced 5 successful initia-tions. At this time it is not known what the reason for this was (e.g., statistical chance, or some dif-ference in the electric matches or in the LTT). The setup used to determine the capacity for initiation of LTT using electric matches was the same as for visco fuse. (See middle illustration in Figure 6.)

The trials using various stronger initiation sources were all successful. These methods in-cluded the use of a more powerfully functioning electric match (Martinez Specialties E-Max elec-tric match[9]) (35 initiations in 35 trials); capaci-tive discharge spark gaps[14] using an 8 J capaci-tive discharge firing set (30 initiations in 30 tri-als); an E-Max electric match coupled to the LTT using a Martinez Specialties Quick-Fire VF clip[13] (3 initiations in 3 trials); commercial exploding bridgewire initiators (Martinez Specialties) using an 8 J capacitive discharge firing set (3 initiations in 3 trials); hand-made exploding bridgewire initi-ators (a bare electric match tip, without any pyro-technic composition) using an 8 J capacitive dis-charge firing set (3 initiations in 3 trials), CCI #209M shot shell primer using a commercial shock tube firing appliance (3 initiations in 3 tri-als) and functioning commercial shock tube (2 initiations in 2 trials). In all cases, the setup in these initiation trials was as described above.

In the case where the initiation source was vis-co fuse augmented with a small flash powder charge, the coupling method was similar to that used for visco fuse. However the length of tubing was extended to approximately 32 mm (1-1/4 in.) in length and a small amount (approximately 50 mg) of flash powder was added to the tubing be-tween the initiation source and the LTT. (See the

lower illustration in Figure 6.) The flash powder used in these trials was 70:30 potassium perchlo-rate and dark pyro aluminum (–400 mesh).

LTT Coupling Methods

One of the standard (and effective) methods used to couple lengths of shock tube is to insert the ends to be joined together into a short length of inert tubing. (This coupling method is demon-strated in the top photograph of Figure 7.) Provid-ing the two ends of tubing are reasonably close together inside the coupling tube, communication of the shock reaction seems assured. However, because the coupling tube is inert, there is a lim-ited gap length between the two shock tube ends

Tubing

LTT

Compression Fitting

Gap

LTT

LTT

Clear Tubing

LTT

Cable Tie

Tight Bend

Figure 7. A photograph demonstrating the LTT “direct contact” in inert tubing (top), “compres-sion fitting” (upper middle), and “gap” (lower middle) coupling methods. Also shown is the “very tight bend” (bottom) used in a propagation test. [0.1 in. per division.]


that will still provide reasonably assured commu-nication of the shock reaction.[15] The testing of LTT took two forms: 1) to verify that LTT can be effectively coupled using the same general end-to-end method that is effective for conventional shock tube, and 2) to establish the approximate maximum gap that will provide reasonably as-sured propagation of LTT’s pyrotechnic reaction. A summary of the test results is presented in Ta-ble 3. In each case, the length of LTT before the coupling was approximately 300 mm (12 in.), to allow for the full development of LTT’s propagat-ing reaction.

In the coupling trials with the ends of two lengths of LTT in direct contact inside a short length of slightly larger inert tubing (upper photo-graph in Figure 7) a total of at least 30 trials were attempted and all successfully propagated the LTT reaction.

In addition to the coupling trials using inert tubing, trials were also conducted using metal compression fittings (upper middle photograph in Figure 7) and reusable plastic compression fittings (not shown). By design, these fittings operate with a short gap between the ends of the tubing being coupled. In the metal fitting the gap was approxi-mately 5 mm (0.2 in.) and in the plastic fitting the gap was approximately 12 mm (0.5 in.). While the fittings could have been drilled out to allow the end of the LTT to be in close end-to-end contact, this would have been an inconvenience and was anticipated to be unnecessary. This is because LTT should be capable of successfully propagat-ing through a short length of an inert coupler. In a limited number of trials (1 using a metal fitting and 5 using plastic fittings), all trials were suc-cessful.

Table 3. A Summary of the Results from the Testing of LTT Coupling Methods.

Test Conditions(a) Successes

/ Trials

Direct contact, end to end cou-pling using inert tubing(b)

30 / 30

Coupled using metal compression fittings(c) 1 / 1

Coupled using plastic compression fittings 5 / 5

Coupled through ≈ 18-mm (3/4-in.) inert tubing gap(d,e)

2 / 2

Test Conditions(a) Successes

/ Trials

Coupled through ≈ 38 mm (1-1/2-in.) inert tubing gap(d,f)

10 / 10

Coupled through ≈ 51-mm (2-in.) inert tubing gap(d)

3 / 7

Coupled through ≈ 76 mm (3-in.) inert tubing gap(d)

0 / 3

Propagating through very tight bend(g) 2 / 4

a) Unless otherwise stated, to allow for the full devel-opment of LTT’s propagating reaction, approxi-mately 300 mm (12 in.) of LTT was included be-fore attachment to a coupling tube. This allowed for the full strength of the LTT propagation reaction to be fully established. Trials were conducted at a temperature of approximately 15 °C (60 °F) and a relative humidity of less than 40%.

b) See the upper photograph in Figure 7 for an illustra-tion of the “direct contact” coupling method used.

c) See the upper middle photograph in Figure 7 for an illustration of the “compression fitting” coupling method used.

d) See the lower middle photograph in Figure 7 for an illustration of the “gap” coupling method used.

e) See Figure 8 for a composite series of photographs of the propagation the LTT reaction through an ap-proximately 18-mm (3/4-in.) gap.

f) See Figure 9 for a composite series of photographs of the propagation the LTT reaction through an ap-proximately 38-mm (1-1/2-in.) gap.

g) See the lower photograph in Figure 7 for just how tight a bend was attempted.

Next a series of trials were conducted to de-termine the approximate maximum gap that would provide reasonably reliable propagation of the LTT reaction. In these trials, the ends of two lengths of LTT were inserted into a length of inert tubing with an inside diameter the same as the outside diameter of the LTT (see the lower middle photograph in Figure 7). The two ends of the LTT were left separated within the larger diameter tub-ing by distances of approximately 18, 38, 51 and 76 mm (3/4, 1-1/2, 2 and 3 in.). All of the trials using the approximately 18 and 38 mm (3/4 and 1-1/2 in.) gaps were successful in propagating the LTT reaction. However, in viewing the propaga-tion using high frame-rate video[16] it seemed ap-parent that the approximately 38 mm (1-1/2 in.) gap was near the maximum gap that could be tol-erated. This can be seen by comparing Figures 8 and 9, high frame rate video of the propagation


through approximately 18 and 38 mm (3/4 and 1-1/2 in.) gaps, respectively. For the approximately 18 mm (3/4 in.) gap (Figure 8) there is only a sin-gle image (0.0001 s) in the sequence of images before the propagation of the LTT reaction was reasonably fully reestablished after reaching the gap. To the contrary, for the approximately 38 mm (1-1/2 in.) gap (Figure 9) eight images lapsed before the propagation is reasonably fully reestablished after reaching the gap. Note in Ta-ble 3 that when the gap was increased to approxi-mately 51 mm (2 in.), propagation was only suc-cessful in three of seven trials, and when the gap was further increased to approximately 76 mm (3 in.), none of three trials were successful.

Figure 8. A collection of 6 images of the propa-gation of LTT through an approximately 18 mm (3/4 in.) gap. The elapsed time between images is 0.0001 second.[16]

Tight Bend Propagation Test

The ability of LTT to propagate through an ex-tremely tight bend was briefly investigated. The tightness of the bend is documented in the bottom photograph of Figure 7, and it approximates the very tightest bend imaginable for LTT. It was found that two of four trials were successful;

however, the number of tests was so small as not to be definitive.

LTT Branching Methods

A series of trials were performed to help estab-lish the ability of LTT line to successfully branch (split) into two or more LTT lines. The results are summarized in Table 4 and discussed in more de-tail below.

Figure 9. A collection of 12 images of the propa-gation of LTT through an approximately 38 mm (1-1/2 in.) gap. The elapsed time between images is 0.0001 second.[16]


Table 4. A Summary of the Results from the Testing of LTT Branching Methods.

Test Conditions(a) Ignitions / Trials

Into the mid-branch of a single tubing-tee(b,c) 10 / 10

Into a side-branch of a single tubing-tee(b,d)

4 / 4

Through a tubing-tee into two additional tubing-tees(b,e)

10 / 10

Through a tubing-tee with only ≈ 76 mm (3 in.) of LTT leading to two additional tees(b,e)

9 / 10

Through a tubing-tee directly (no LTT) into two additional tubing-tees(b)

0 / 4

Through a reusable plastic compression fitting tee(f) 3 / 3

Through a single-use metal compression fitting tee

1 / 1

Propagating through a notched LTT(g) 8 / 8

Split into three lines by coupling a pair of notches(h) 2 / 2

Split into seven lines by coupling inside inert tubing(i)

2 / 2

a) Unless otherwise stated, to allow for the full devel-opment of LTT’s propagating reaction, approxi-mately 300 mm (12 in.) of LTT was allowed before attachment to a tee or the first notch. This allowed the full strength of the LTT reaction to be estab-lished before branching. Trials were conducted at a temperature of approximately 15 °C (60 °F) and a relative humidity of less than 40%.

b) See the upper photograph in Figure 10 for an exam-ple of LTT branching through a tubing tee.

c) See the upper illustration in Figure 11 for the orien-tation of the tubing tee in these trials.

d) See the lower illustration in Figure 11 for the orien-tation of the tubing tee in these trials.

e) This arrangement is illustrated in Figure 12.

f) See the middle photograph in Figure 10 for an ex-ample of LTT branching through a compression fit-ting tee.

g) See the lower photograph in Figure 10 for an exam-ple of a notch made into LTT and the lower photo-graph in Figure 13 for the fire output from notches in a LTT line being fired.

h) See Figure 14 for photographs of this LTT splitting method.

i) See Figure 15 for a photograph of this LTT splitting method.

The first branching method tried used standard tubing tees coupled as shown in the upper photo-graph of Figure 10. The attachment of LTT to the tubing tees was accomplished using short lengths of inert tubing. In the first trials, the LTT propa-gating reaction entered the middle branch of the tee, after traversing a total gap length of approxi-mately 24 mm (0.95 in.) of inert tubing tee plus having negotiated a 90° bend (see the upper draw-ing in Figure 11). Ten of ten trials of this branch-ing method successfully propagated the LTT reac-tion. Further testing was performed using a slight modification of this tubing tee method, where the LTT propagation reaction entered one of the side-

Tee Tubing

Notch

Plastic Tee

LTT

LTT

LTT

Figure 10. Photographs demonstrating three of the LTT branching methods used in this study. [2.5 mm (0.1 in.) per division.].


branches of the tee (see the lower drawing of Fig-ure 11). Four of four trials of this branching meth-od were successful in propagating the reaction.

LTT Feed Line LTTOutputLines

LTT Feed Line

LTTOutputLines

Figure 11. Illustrations of the configurations used for the testing through a single tee: upper, LTT reaction enters through middle-branch of the tee; lower, LTT reaction enters through one side branch of the tee.

In the next series of trials, the pair of outputs from the one tee were sent into two additional tees for additional branching into a total of four LTT lines (see Figure 12). When the LTT lines be-tween the first and the additional tees was approx-imately a full 300 mm (12 in.), ten of ten trials successfully propagated the LTT reaction. How-ever, when the length of LTT between the tees was reduced to approximately 76 mm (3 in.), only nine of ten trials were successful. When the three tees were coupled directly together with no LTT between the tees, none of four trials were success-ful. Note that this is consistent with the gap test-ing, where it was found that the maximum gap providing relatively reliable propagation of the LTT reaction was approximately 76 mm (1.5 in.). The use of additional tees coupled directly to the first tee requires the LTT reaction to traverse ap-proximately 48 mm (1.9 in.) plus negotiate two 90° bends.

The next series of trials involved only a very slight modification of the tubing tee trials, in these tests compression tees were used (see middle pho-tograph of Figure 10). In trials with plastic com-pression tees, three of three were successful. A

single trial with a metal compression tee was also successful.

Another branching method tried consisted of simply cutting a series of notches into lengths of LTT using a standard hand-held paper punch. A typically produced notch is shown as the bottom photograph in Figure 10. (Even though it is thought to be highly unlikely that punching notch-es in the LTT would cause its initiation, it is ap-propriate to employ all of the ordinary precautions that one would use in cutting any type of fuse.) Figure 13 consists of two images taken from a standard frame-rate video recording, demonstrat-ing the basis for trying this method of branching. The upper image shows a length of LTT with a series of 5 paper punch notches prior to firing the LTT. The lower image shows the fire-spit from the five notches as the LTT fires. In eight of eight trials, LTT successfully propagated through a se-ries of notches separated by 100 mm (4 in.) pro-ducing significant fire spit at each notch. While the arrangement shown in Figure 13 is of essen-tially no use in itself, it can be useful in: a) branching to additional LTT lines, and b) igniting pyrotechnic compositions if a charge of powder is positioned in the immediate area of each notch.

Using the notch method for branching is demonstrated in Figure 14. In this method, a notch was first cut into two LTT lines using a paper punch. The two notches were placed over each other (notch to notch) and held on a small piece of tape. The two LTT lines were further secured us-ing a second piece of tape. Only two trials using

LTT Feed Line

LTTOutputLines

Tees LTTOutputLines

Figure 12. An illustration of the configuration used for the testing through multiple tees.


this method were attempted and both were suc-cessful. While easy to accomplish, this notch splitting method divides one LTT input line into

three output lines.

Another method for branching was attempted in which the input LTT line was split into seven output lines (see Figure 15). This method used a short length of inert tubing with an internal diame-ter just large enough to accommodate the seven output LTT lines, which were inserted a short dis-tance into the coupling tube. The input LTT line was fit through a sleeve that was large enough to fit securely into the larger diameter inert tubing. The input and output LTT lines were separated by approximately 5 mm (0.2 in.) inside the coupling tube. Again only two trials were attempted using this method and again both were successful.

LTT Ignition Capabilities

One of the attractive characteristics of LTT is its ability to ignite typical pyrotechnic composi-tions directly (i.e., without using the shock-to-flame converters needed with conventional shock

Figure 15. A Photograph demonstrating one possible multiple branching method using a coupling tube. [2.5 mm (0.1 in.) per division.]

Figure 14. Photographs demonstrating a possible LTT branching method using the “notch” method. [2.5 mm (0.1 in.) per division.]

Notches

Figure 13. Two images demonstrating the basis for trying the notch method of branching and fire spit produced from a series of 5 notches approxi-mately 100 mm (4 in.) apart in a length of LTT. The upper image is of the LTT hot melt glued to a support with pieces of tape below marking the location of each notch. The lower image docu-ments the fire spit from the notches when the LTT was fired.


tube). The results from the ignition trials are summarized in Tables 5 and 6 and are discussed further below.

The first series of trials was conducted to de-termine the ability of LTT to ignite various pyro-technic fuses. When the fuses were of approxi-mately the same diameter as the LTT, both the LTT and fuse were inserted a short distance into a length of 3 mm (1/8 in.) internal diameter (ID) inert tubing. This is illustrated in Figure 16 for coupling to visco fuse (also called hobby, cannon or fireworks safety fuse). This method was tried using a medium quality visco fuse (10 trials), fast burning visco-like fuse such as used on reloadable consumer firework aerial shells (4 trials), and both Thermolite (4 trials) and Mantidor (10 trials) ig-niter cords. In each case, all trials were successful in igniting the various fuse types.

ViscoFuse

CouplingTube

LTT

Figure 16. An illustration of the inert tube cou-pling method used to ignite the visco fuse and oth-er small diameter pyrotechnic fuse types.

The inert coupling tube method was also tried using a reasonably high quality firework time fuse. However, in this case, because of the larger diameter of the time fuse, a 6 mm (1/4 in.) ID in-ert coupling tube was used. For the LTT to be rea-sonably well secured into the larger diameter cou-pling tube, the end of the LTT was first fitted into a very short length of a spacer tube to enlarge its effective outside diameter from 3 to 6 mm (1/8 to 1/4 in.). Three of three trials produced successful ignitions.

One potential drawback of the coupling tube method described above (as in Figure 16) is that it terminates the LTT line, which is then not availa-ble to produce more than the single ignition. Thus a variation of the notch branching method was tried. This method employed a notch cut into the side of the LTT using a paper punch. The end of the fuse to be ignited was positioned against the notch and then held in place using tape. In the first of these trials visco fuse was used, as shown in the upper pair of photographs of Figure 17. In these trials, four of four fuse ignitions were successful.

The lower pair of photographs in Figure 17 is a similar notch coupling method this time using quick match with a short length of black match exposed. After the notch was made in the LTT, the black match was laid into the notch, folded back over the LTT and secured with 50-mm (2-in.) wide plastic packaging tape. In these trials, five of five fuse ignitions were successful.

Figure 17. Photographs demonstrating the notch method of coupling fuse to LTT. The upper pair of photographs used visco fuse and the lower pair used a short length of black match from a shell leader. [2.5 mm (0.1 in.) per division.]

A final series of fuse ignition trials was at-tempted in which the end of the LTT was simply inserted into quick match either into the end of a length of quick match or through a small hole made in the match pipe somewhere along the length of quick match. Using either method, care was taken to assure that the end of the LTT was immediately alongside the black match in the shell leader. Shell leaders from three manufactur-ers (Thunderbird, Jumping Jack and Sunny) were used in these trials, where 14 of 14 attempts to ignite quick match were successful.

Having completed the trials of fuse ignition, LTT’s ability to directly ignite a variety of pyro-


technic compositions was investigated. The results of these trials are presented in Table 6. In those trials, the powders, whether loose or granulated, were placed in a small container and the end of the LTT was introduced a short distance into the

powder charge, as shown in Figure 18. The first powder type to be investigated was Black Powder. These trials used 3Fg, 4FA, 2FA commercially manufactured powder, loose fine-grained hand-made Black Powder, and Black CanyonTM powder (a commercial Black Powder substitute based on ascorbic acid as the primary fuel). In these trials, all 42 of 42 attempts produced successful igni-tions of the powders.

LTT

Pyrotechnic Composition

Plastic Container

Figure 18. An illustration of the test method used in the trials of LTT ignition of loose pyrotechnic powders.

One potential drawback of the direct insertion method described above (as in Figure 18) is that it terminates the LTT line, which is then not availa-ble to produce additional ignitions. Thus a varia-tion to the direct insertion method was tried. In one trial of the ignition of small charges of Black Powder, a series of four small mortar tubes were mounted over a single length of LTT (see Fig-ure 19). At the location of each tube, a notch had been cut in the LTT with a hand-held paper punch. The distance between notches was approx-imately 100 mm (4 in.). A small charge of 4FA Black Powder and a projectile were added to each of the four small mortar tubes. Upon firing the single LTT line, all four Black Powder charges were simultaneously ignited and successfully fired the four small projectiles into the air.

Figure 19. A photograph of the test configuration for simultaneously firing four small mortars from a single LTT line running under the mortars in a grove cut into the mounting board.

Next, two types of flash powder were used in the ignition trials. Both flash powders were of

Table 5. Results of Testing LTT’s Ability to Directly Ignite Various Types of Pyrotechnic Fuse.


Coupled to medium quality visco fuse(b) 10 / 10

Coupled to fast burning visco-like fuse such as used on reloadable consumer firework shells(b)

4 / 4

Coupled to fast ThermoliteTM igniter cord(b)

4 / 4

Coupled to MantidorTM plastic igniter cord(b)

10 / 10

Coupled to firework time fuse(b,c) 3 / 3

Coupled to medium quality visco fuse using a notch(d) 4 / 4

Coupled to quick match shell lead-er (Jumping Jack brand) using a notch(d)

5 / 5

Inserted into quick match shell leader(e) 14 / 14

a) To allow for the full development of LTT’s prop-agating reaction, in each trial an approximately 300 mm (12-in.) length of LTT was provided be-fore its attachment to a pyrotechnic fuse. Trials were conducted at a temperature of approximately 15 °C (60 °F) and a relative humidity of less than 40%.

b) In each case the LTT was coupled to the fuse us-ing a short length of 3 mm (1/8 in.) ID inert tub-ing, for example see Figure 16. The ends of the LTT and fuse were in contact or near contact within the coupling tube.

c) In the case of coupling LTT to firework time fuse, a 6 mm (1/4 in.) ID inert coupling tube was used and the LTT was fit into a sleeve to increase its OD to fit securely into the coupling tube.

d) This notch method is demonstrated in Figure 17.

e) In these trials, the LTT was either inserted into the end of a length of the quick match or through a small slit made in the match pipe, such that the LTT was immediately alongside of the black match. Shell leaders from three manufacturers (Sunny, Thunderbird and Jumping Jack) were used in these trials.


standard formulations. One was a mixture of po-tassium perchlorate (70%) and dark-pyro alumi-num (30%), and the other flash powder was a mixture of barium nitrate (58%), dark-pyro alu-minum (28%), and sulfur (14%). Again the end of the LTT was placed into a small charge of the powder (see Figure 18). In these trials, all six of six attempts produced successful ignitions.

One type of smokeless powder (IMR 7828) was used in the ignition trials. This type of smoke-less powder was chosen only because it was im-mediately available in the laboratory. It is a rather coarse powder and is somewhat unlikely to be chosen for most entertainment pyrotechnic uses. Only four of ten attempts with this powder were successful. As a result, if it were desired to relia-bly ignite such fairly large particle size smokeless powders (and perhaps others as well) it is likely that the output of the LTT would need to be aug-mented, such as perhaps by first igniting a small charge of Black Powder.

As a final trial, the ignition of three small whistles (Pyropak, manufactured by Luna Tech, Inc.[12]) was attempted. In these attempts, the end of the LTT was simply inserted into the end of the whistle tube, such that the end of the LTT was in near contact with the compacted whistle composi-tion. The LTT was temporarily held in place with-in the whistle using a small plug made of wadded-up tissue paper. All three whistle ignition trials were successful.

Conclusion

While the number of trials reported in this pa-per give some indication of the capabilities of Lightning Thermo Tube (LTT), often the number of individual trials was not statistically significant. This not withstanding, it seems reasonably certain that LTT is a useful product and will find a num-ber of uses in fireworks and proximate audience pyrotechnics. Probably the most desirable features of Lightning Thermo Tube (LTT) are:

• Its ability to be reliably initiated using rea-sonably energetic electric matches (without having to use flame-to-shock converters).

• Its ability to reliably ignite typical pyrotech-nic fuses and powders (without having to use shock-to-flame converters).

• Its ability to produce a bright flash of light (with or without a fairly loud explosive sound).

Table 6. Results of Testing LTT’s Ability To Ignite Various Pyrotechnic Powders Directly.


3Fg Black Powder(b) 4 / 4 4FA Black Powder(b) 14 / 14 2FA Black Powder(b) 10 / 10 Unconsolidated (loose) hand-made Black Powder(b,c)

4 / 4

Black CanyonTM 2Fg powder (a Black Powder substitute)(b)

10 / 10

4FA Black Powder(d) 4 / 4

7:3 flash powder (potassium perchlorate and dark aluminum)(b,c)

3 / 3

4:2:1 flash powder (barium nitrate, dark aluminum and sulfur)(b,c)

3 / 3

IMR 7828 smokeless powder(b,e) 4 / 10

Pyropack 2-second titanium whistles(f) 3 / 3

a) To allow for the full development of LTT’s propa-gating reaction, in each trial an approximately 300 mm (12-in.) length of LTT was provided before its attachment to a pyrotechnic powder. Trials were conducted at a temperature of approximately 15 °C (60 °F) and a relative humidity of less than 40%.

b) In the trials to ignite loose pyrotechnic powders, a small container, typically 12 by 50 mm (0.5 by 2 in.) was filled with the test powder. The LTT en-tered into the container through a hole, with the end of the LTT positioned a short distance into the powder charge. (See Figure 18.)

c) This powder was sufficiently fine grained that a small amount of powder might possibly have en-tered into the end of the LTT. In the event that such powder infusion needs to be avoided, the US dis-tributor of LTT[1] suggests that the end of the LTT can first have a thin coat of nitrocellulose lacquer applied over the hole in the end of the LTT.

d) In this trial all four charges of Black Powder were simultaneously ignited using 4 notches cut into a single length of LTT (discussed further in the text).

e) This type of smokeless powder was chosen only because it was immediately available in the labora-tory. It is a rather coarse powder and is somewhat unlikely to be chosen for most entertainment pyro-technic uses. It is quite possible that a finer grained powder would be more readily ignited by LTT.

f) In this case the end of the LTT was inserted into the end of the whistle tube with the end of the LTT in near contact with the whistle composition and tem-porarily held in place with a small wad of tissue pa-per.


• Its resistance to accidental ignition due to strong impact and high temperature flame.

• Its ability to be coupled and branched using the same methods commonly used for shock tube.

• Its non-hazardous classification for transpor-tation.

In considering the results reported in this pa-per, it is important to note that all trials were con-ducted at a temperature of approximately 15 °C (60 °F) and a relative humidity of less than 40%. Certainly, it is possible that the performance of LTT under more extreme conditions may be dif-ferent. Thus further testing under more adverse conditions would be appropriate.

While there undoubtedly are many potential uses for LTT in fireworks and proximate audience performances, and while this paper may have put readers in mind of some applications, it was not the purpose of this paper to suggest or recommend any specific applications for LTT.

Acknowledgments

The authors are grateful to R. Webb for sup-plying some patent and background information about thermo-tube, to R. Gilbert for supplying samples of LTT for evaluation, and to E. Con-testabile and L. Weinman for commenting on an earlier draft of this paper.

Notes and References

1) Trademarked and distributed in the US by Lightning Thermo Tube, 12707 N. Freeway, Suite 330, Houston, TX, 77060, USA.

2) “Process for the Production of a Thermal Shock Tube”, M. A. Falquete, US Patent Number 205/0109230 A1.

3) “Low Energy Fuse for Transmission or Gen-eration of Detonation”, P. A. Persson, Swe-dish patent 333 321, July 20, 1968.

4) “Wherl Element”, P. A. Persson and G. Lith-ner, US patent 3-817-181, Jan. 5, 1972, granted Jan. 18, 1974.

5) A New Non-Electric Blasting System – NONEL, E. Contestabile, Energy Mines and Resources Canada, MRL/75-20, 1975.

6) In the 1990s in the US a product called No Match™ and intended for the firework trade, was introduced. No Match was based on conventional shock tube as used in the blast-ing industry. However, to facilitate its use in fireworks, it required flame-to-shock initia-tors for use with pyrotechnic fuse or electric matches, and shock-to-flame converters for reliable ignition of pyrotechnic materials.

7) Lightning Thermo Tube, Draft Technical Data Sheet, Sept. 2005.

8) The high frame-rate video camera was pro-vided by Speed Vision, San Diego, CA, USA.

9) Martinez Specialties, Inc., 205 Bossard Rd., Groton, NY 13073, USA.

10) Material Safety Data Sheet, IBQ Industrias, Quimicas, Ltda, Quatro Barras, PR, Brasil.

11) “Classification of Explosives”, US Depart-ment of Transportation, Tracking Number 2005030367, 2005.

12) Luna Tech, Inc., Owens Cross Road, USA.

13) “Evaluation of ‘Quick-Fire’ Clips”, K. L. and B. J. Kosanke, Fireworks Business, No. 263, 2005; Selected Pyrotechnic Publications of K. L. and B. J. Kosanke, Part 8 (2005 through 2007), Journal of Pyrotechnics, 2009.

14) “Electric Shock Tube Firing Systems”, K. L. Kosanke, American Fireworks News, 156, 1994; also in Best of AFN III, American Fireworks News, 1995; Selected Pyrotechnic Publications of K. L. and B. J. Kosanke, Part 3 (1993 and 1994), Journal of Pyrotechnics, 1996.

15) In one study of the ability for conventional shock tube to propagate its reaction through various lengths of inert tubing, it was found capable of spanning a length of nearly 200 mm (8 in.).[5]

16) The collections of photographs in Figures 8 and 9 were produced using a frame-rate of 20,000 fps; however, only every other photo-graph is included in the two figures. This was done to limit the size of the figures for publi-cation.

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